That figure was crunched by Jamais Cascio, futurist and co-founder of WorldChanging.com, who blogs at Open the Future. His Cheeseburger Footprint figure actually became quite popular, used in media outlets around the world and even appearing in the National Geographic documentary Six Degrees.

And now, you can wear the figure on your chest. Organic cotton T-shirts bearing Cheeseburger’s uneco numbers in a nutrition label-like format are available through Open the Future’s CafePress store. For $23.99, you can wear a T-shirt to motivate your own green eating habits, to edify others about their diet choices — or simply to scare people smart enough to know global climate change is real but who are in denial enough to keep eating factory farmed beef.

If you’re confused as to why the number on the shirt (5.18 kg) doesn’t match the number used in the calculations in Jamais’ blog post (4.35 kg), it’s because the actual cheeseburger footprint figure that Jamais calculated is a range: 3.6 – 6.1 kg of CO2-equivalent per burger. Jamais says the 4.35 figure is just a number within the range used for a sample calculation, while 5.18 is the number within that range picked for the T-shirt “because it looked good.”

Good enough to wear as a T-shirt — but not to eat as a burger! There’s a Cheeseburger Footprint reusable tote bag too, and fittingly, an apron. Those are made with conventional cotton, which has its own gigantic environmental footprint — but may still prove irresistible to eco-foodie cooks who've wanted to ask their less green friends “How do you want your carbon crime grilled?” — followed by an evil laugh. Mwahahaha!